Natural penicillin is a well-known antibiotic isolated from the mold Penicillium luteum purpurogenum. Many penicillins are now known, each with a different R group in the formula: ##STR3## Perhaps the most widely known penicillin is benzylpenicillin (or penicillin G), in which the R group is: ##STR4##
Other known derivatives include the ampicillins, in which the amino group is acylated by isocumarine-3-carboxylic acids, Bulgarian Inventors Certificate 34 532, and/or (2H)phthalazinone-4-carboxylic acids, Japan Pat. No. 7,873,593. These derivatives are active against Ps. aeruginosa.